Weighing scale pendulum



April 8, 1952 1.. s. WILLIAMS 2,592,499

WEIGHING SCALE PENDULUM Filed May 3, 1946 4 Sheets-Sheet 1 IN VEN TOR.

B g- I I Lawrence .2 W/W/ams ATTORNEYS April 3, 1952 s. WILLIAMS2,592,499

WEIGHING SCALE PENDULUM Filed May 3, 1946 4 Sheets-Sheet 2 INVENTOR.Lawrence S. MV/iams ATTORNEYS April 8, 1952 SMWILLIAMS 2,592,499

WEIGHING SCALE PENDULUM Filed May a. 1946 4 Sheets-Sheet 5 I l I I I I II I I I I Q nvmvrm Lawrence .2 MW/oms L. s. WILLIAMS WEIGHING SCALEPENDULUM April 8, 1952 4 Sheets-Sheet 4 Filed May 3, 1946 d m m w v Qvvv207147/0/4/ 0/ PEA 004 UM mmvrox. Lawrence J. W/'///'a/rzs 'A TORNEYSPatented Apr. 8, 1952 WEIGHING SCALE PENDULUM Lawrence S. Williams,Toledo, Ohio, assignor to Toledo Scale Company, Toledo, Ohio, acorporation of New Jersey Application May 3, 1946, Serial No.667,082

6 Claims. (01. 265-62) This invention relates to weighing scales andmore particularly to pendulums which are used as counterbalancingelements in weighing scales.

Pendulums for use in weighing scales may be divided into two broadclasses, commonly called fixed center pendulums and floating pendulums.A fixed center pendulum is one which is pivoted at its turning center sothat it rotates without translation under the influence of a load to beweighed. A floating pendulum is one that is mounted so that its movementunder the influence of a load to be weighed is a combination of rotationand translation.

A floating pendulum as it is commonly constructed is provided with apair of fulcrum sectors concentric with respect to the turning center ofthe pendulum in lieu of knife edges or other bearings. The pendulum issuspended at the side of a rigid framework, called a sector guide, bysteel ribbons attached to the guide and to the lower ends of the fulcrumsectors. Loads are applied to the pendulum by means of a power ribbonthat overlies an arcuate surface of the pendulum assembly commonlycalled a power sector. When increments of load are applied to the powerribbon of a floating pendulum it rotates about its turning center andthe turning center is translated upwardly a distance determined by theradius of the fulcrum sectors and the angles through which the pendulumturns. Either the upward translation of the turning center or thedownward movement of the power ribbon may be used as a measure of theload. The floating pendulum has an advantage over a fixed centerpendulum because the ribbons supporting the pendulum are not subject towear or friction which would adversely affect the accuracy of theindication.

To provide for adjustment, a floating pendulum, whether the upwardtranslation of the pendulum or the movement of the power ribbon is usedas a measure of load, usually is provided with a threaded stem alongwhich a weight may be moved and means for changin the angular relationof the threaded stem with respect to the sectors. The earliest design offloating pendulum employed a threaded stem which was vertical and inline with the fulcrum ribbons when the indicator was at zero. Itdiffered from a fixed center pendulum only by the substitution of thefulcrum sectors and ribbons for the pivotal mounting of the fixed centerpendulum. Such early pendulum counterbalances were diflicult to adjustbecause it was necessary to make simultaneous corrections of the poweror capacity (diiference in load or pull exerted by the pendulum at theends of its travel) and straightline adjustment. (Straight lineadjustment is that adjustment which gives correct half capacityindication when the scale is adjusted for correct zero and full capacityindication.) These adjustments were interrelated in that no change couldbe made in one of the adjustments without aifecting the other.

For convenience in commercial production and sector guide design thedownward and in-' ward travel of these early floating pendulums waslimited so that the threaded stem and the weight thereon would clear thesector guide when the indicator stood at zero. This change, while itfacilitated the manufacture. and assembly of the entire weighingmechanism, increased the difiiculty of adjusting the scale to securecorrect indications because the initial pull was changed by eitheradjustment. The initial pull of a pendulum is the pull exerted on thepower ribbon or steelyard rod when the pendulum is in its zero net loadposition. The initial pull is used to support the lever system and thedead load of the load receiver.

The next development in floating pendulum design was to return thethreaded stems to vertical at zero, so that the initial pull at zerowould not be changed by movement of the weight along the threaded stem,and to relocate the threaded stem so that its axis passed between theturning center of the pendulum and the periphery of the fulcrum sectorsand far enough from the plane of the fulcrum ribbons so that the weighton the stem would not interfere with the sector guide. This designallowed the position of the weight to be adjusted through a considerablerange without alterin or adjusting the bumpers used to stop the pendulumwhen it swung through the vertical position. This floating pendulum,while an improvement over the earlier floating pendulum, was stilldifiicult to adjust because any movement of the weight along thethreaded stem to correct an error at full capacity required a chan e inangular position of the threaded stem with respect to the sectors tomaintain a correct half capacity indication. One disadvantage of thisfloating pendulum from a manufacturing standpoint is the difliculty ofsecuring adjustment and rigidity between the threaded stem and thesector assembly. The disadvanstages from an adjusting standpoint comenot only from the interaction of the adjustments one upon the other, butalso from the fact that any adjustment of the angular relation betweenthe ings.

sector and the threaded stem causes the sector to assume a new angularposition for a given load. This means that either the indicator must bemoved on its shaft or the connection between the turning center of thependulum and the indicator must be adjusted. In many scales lookingmeans to hold the pendulums .at zero when the scale moved are includedin the structure. These locking means must also be adjusted every time asubstantial change in the angular relation between the threaded stem andthe sectors is made.

The principal object of this invention is to provide a pendulum in whichthe adjustments are substantially independent of eachother.

Another object of the invention is to provide a weighing scale pendulumin which the correct adjustment of one adjusting means may be effectedeven though another adjusting means is still. subject to a substantialerror. v

.- .A stilliurther object of the inventicnis to provide a;fioatingipendulum which is adjusted by the translation of weights alongpaths that are fixed. with respect to the turning center of thependulum.

..A still further object of the invention is to trio power sector inwhich the adjustments are made by the translation of weights along pathsthatare; fixed with respect to the sectors of the pendulum.

[Yet another object of the invention is to provide apenclulum for aweighing scale which pendulum comprises. a frame having integrally.iormed fulcrum and power sectors and a track along. whichan adjustingweight may be moved. .These. and other objects and advantages .are

-..Dro.v,ided by an improved pendulum, examplesoi Whichare illustratedin the accompanying draw- ;i'I'heinvention consists of a floatingpendulum 'The improved pendulum, examples of which qar'ejillustrated inthe accompanying drawings, is" the result of my discovery that when afloating pendulum is adjusted to different capacif ties" by moving aweight along a threaded stem and making the corresponding adjustments intheangular relation between the stem and the sectors,.thecenter ofgravity of the pendulum 'moves along a straight line bearing a definiteangular relationship with respect to the sector assembly. The line orlocusv along which the ,center of gravity moves when the capacity of"the pendulum is varied passes on that side of theturning center of thependulum opposite the "fulcrum and power sectors.

When the pendulum is, constructed so that the capacity adjust- 1 ingweight is movable along a track parallel to the locus of the centers ofgravity, the move- --ment of the weight alters the capacity of thependulum and simultaneously changes the angular relation of the centerof gravity with respect to the sectors to provide the required straightline correction. This automatic change in-angular-relationship verymaterially simplifies the adjustment of the pendulum.

I have also discovered that the straight line correction for a pendulummay be made without affecting the capacity adjustment when a secondweight is-moved along a track bearing a i 4 definite angularrelationship with respect to the track along which the capacityadjustment weight is moved. The movement of the second weight, to eifecta straight line adjustment,- changes the initial pull of the scale. Inthe improved pendulum this change in initial pull is a fixed multiple ofthe straight line correction obtained, by moving the weight. Thereforethe straight line correction may very easily be made by noting thechange in indication of the scale at half capacity as the adjustingweight is moved. Penduluins designed according to these discoveries,offermany advantages over the previous pendulurns 'becausenot only arethe adjustments substantially independent of each other but also theangular adjustment of the sectors with re- .spects tothe. pendulum stemcan be eliminated provide. av floating pendulum having an eccenimodified form ofrthe invention.

' housing I.

so that a much lighter, more rigid pendulum may be made. The eliminationof the angular adjustment also eliminates any need for the adjustmentsin the indicator connection and in the locking mechanism. It is alsopossible to select a'certain'angle for the initial position of thependulum. so that the initial pull remains constant for all changes ofcapacity'of'the pendulum made by moving the major adjusting weight.

' Examples of pendulums embodying the invention are illustrated in theaccompanyingdrawings.

In the drawings:

Figure I is a front elevation of aload counterbalancing and indicatingmechanism embodying the invention.

Figure 11- is a horizontal section taken substantially along the lineII-'-II of Figure I.

Figure III is an enlarged fragmentary rear elevation of thecounterbalancing mechanism shown in Figure I.

Figure IV is a side elevation partly'in section andv with parts brokenaway of the adjusting weightmounted on. the-pendulum shownin llisureIII.

Figure V is a: fragmentary rear elevation of load 'counterbalancingmechanism embodying a Figure VI-is a plan of the adjusting weightincluding a fragment of the: pendulum as seen r proved pendulums.

These-2 specific; figures and the accompanying description are intended.merelyv to illustrate the invention but not to impose limitations on theclaims.

Load counterbalancing and load indicating mechanism constructedaccording to the invention is contained within a substantiallywatchcase-shaped housing i havin a dial 2 on which are suitablyinscribed a series of indicia 3 in dicating increments of weight. Anindicator 4 rotatable in response to loads being-weighed sweeps over thedial 2 and cooperates with indicia 3 to indicate the magnitude of theload.

A sector guide 5, a framework consisting of four vertical members heldin spaced rectangular relationship by integrally formed cross ties,

is mounted in a vertical position within. the The indicator d is carriedon a shaft that is journaled in bearings mounted in centrally locatedcross webs of the sector guide 5.

A pair of pendulums 8 and 1 each having fulcrum sectors 8 are suspendedon the sides of the sector guide 5 by means of fulcrum ribbons 9 whoseupper ends are attached to the sector guide 5 and whose lower ends areattached to the lowermost ends of the fulcrum sectors 8. The fulcrumsectors 8 correspond in function to the fulcrum pivots of an ordinarylever or fixed center pendulum, and the point of tangency, the take-01fpoint of the fulcrum ribbons 8 from the sectors 8, forms'the'instantaneous center or fulcrum about which the pendulum pivots.

Forces from loads to be weighed are transmitted through a yoke [8attached to the upper end of a steelyard rod H to a pair of powerribbons [2 whose upper ends overlie the peripheries of and are attachedto the upper ends of power sectors l3 of the pendulums 6 and I. Thepower sectors 13 are of greater radius than the fulcrum sectors 8 andextend between the sides of the sector guide 5 so that when load isadded the pendulums tend to swing outwardly and to roll upwardly alongthe sides of the sector guide 5. The motion of the pendulum is thus acombination of rotation and translation which may be resolved into arotation about axes passed through the centers of the fulcrum sectors 8and an upward translation of these axes. In the counterbalancingmechanism illustrated, the translation of the pendulum is used as ameasure of the load. A pair of compensating bars l4 and I5 are carriedon screws 16 and I! that are threaded through the legs of a yoke l8 andwhose conical tips engage ball bearings 18 mounted in the turningcenters of the pendulums 8 and 1. Midway between their ends thecompensating bars l4 and I5 carry a loosely pivoted cross bar 28 fromwhich cross bar a rack 2| is resiliently suspended. The rack 2i mesheswith a pinion on the indicator shaft and serves to rotate the indicator4 through an angle that is proportional to the upward translation of theturning centers of the pendulums 6 and I. Because the rack is suspendedfrom the midpoints of the compensating bars l4 and its motion is theaverage of the upward translations of the pendulums. The pendulumsrotate in opposite directions so that any 'sidewise tipping of the scalewhich causes one pendulum to increase its pull causes an equal loss ofpull of the other pendulum with the result that the total pull, theposition of the rack and the indication remain unchanged.

Each of the pendulums 8 and I is formed from a generally flat castinghaving a thin web 22 (Figures II and III), reinforcing ribs 23 aroundthe periphery and a cross rib 24. The casting has laterally extendingbosses 25 and 26 along its turning axis to provide support for thebearings I9 carrying the compensating bars l4 and [5. The fulcrumsectors 8 are formed as laterally extending cylindrical wall-likesections concentric with respect to the turning axis. The power sector[3 is formed by an arcuate rib at the upper end of the pendulum casting.The surfaces of the sectors over which the fulcrum and power ribbons lieare circular arcs, the fulcrum sectors being concentric with thebearings l9, while the power sectors are concentric with respect to apoint 21 that is displaced from the turning center.

Each of the pendulums has a track 28 formed along one of its edges whichtrack provides ways for mounting an adjusting weight assembly29.

The track'28 is similar to a T-slot except that the bottom of the slotis cylindrical instead of being rectangular as in the ordinary T-slot.The adjusting weight assembly 29, one for each of the pendulums 6 and 1,has a main or primary weight 30 one surface of which is machined andprovided with flanges 3| forming a groove to receive the track 28. Theprimary weight 38, cast of lead or some heavy material, is secured inposition by a pair of bolts 32 that passing through spools 33 enter theslot in the track 28 and are threaded into a cylindrical nut 34 that isslidable along the cylindrical bottom of the T-slot. The spools 33 arecast in the primary weight 30 so that the bolts 32 may be tightenedwithout deforming the weight.

'-A second track is formed by an -L-shaped bracket 35, one leg of whichis secured under the heads of the bolts 32 while the other leg extendsoutwardly in the planeof the pendulum. A secondary weight comprising asubassembly 36 is mounted on the bracket 35. The secondary weightconsists of a U-shaped holder 31 whose legs are notched to slide overthe bracket 35. A slidable subweight 38, a spring clip 39 and a nut 40are mounted within the U-shaped holder 31 and clamped by means of a setscrew 4!. This subassembly is shown in plan in Figure II and in sideelevation in Figure IV. The subassembly 36 is constructed so that whenthe set screw 4! is loosened the parts are frictionally held by thespring clip 39 and the subweight 38 may be moved along a path that isparallel to the track 28 or the whole subassembly 38 may be moved alongthe secondary track formed by the bracket 35.

The solid'lines of Figure III show the pendulum "i in the position thatit occupies when the indicator is at zero, 1. e. with no'load on theweighing scale. In this position the track 28 is vertical and the lineof centers of the fulcrum and power sectors is substantially horizontal.In this position a horizontal flange 42 formed integrally with thependulum is just clear from arresting bumpers 43 projecting from abracket 44 mounted on the sector guide 5 and a locking horn 45 has itstip immediately below an opening 46 of a locking bar 41. The locking bar41 is mounted for vertical movement in the sector guide 5 and is drawndownwardly when the lever mechanism of the scale is locked.

The casting for the pendulum illustrated in Figure III is made ofaluminum and the weight is distributed so that the center of gravity'ofthe pendulum casting and the adjusting weight assembly 29 liessomewhere along the track 28. The location of the track 28 is fixedaccording to the geometry of the sectors and the angle at which thepower ribbon l2 pulls against the power sector l3 so that the linearrelationship between pull in the steelyard rod H and angular rotation ofthe pendulum is maintained for any position of the weight assembly 29along the track 28. Thesubweight 38 and the minor weight assembly 36allow minor adjustments of capacity and linearity to be made after theadjusting weight asseinbly29 has been clamped to the track 28.

' This pendulum offers the advantages that the power or capacity of thependulum, the difference between its pull at full capacity and at zero,may be adjusted through wide ranges by movement of the adjusting weightassembly 29 along the track 28 without changing the initial pull. Thispermits, for example, a hundred pound capacity scale to be changed to atwo hundred pound capacity steamer.

scaleiby; merelyrlowering. the; weights: along; the; tlfilfiksf 'zaj-f-The. "power- .of: the. p n ulum-m nb I varied were useful :range "ofgapproximatelrfi :1 by changing the location; oftheweights alongthetrack :28

. It; ismot necessaryi that; the track along, which theadjusting.weights-aremounted shall be-verti-.=. caliwhen: theindicator-stands at. zero. I The high initialpull. resultingj from; thisvertical condition mayi'be ,rundesirablei for some applications. T einitial: pull-1 may be reduced Without; changing the power ofthe-pendulumby designingthependulum sorthatltmay swingin toward thesectorguide flt-TZIOW loads: initialipull isillustrated in. Figure V.-This fi urecorresponds to Figure IIIand illustrates the pen,-

dulum-asitis seen from the back. of the scale.

A ;'-pendulum designed -fr lower.

In'this example, a pendulum body ld, formedasy a single casting, hasgenerally cylindrical-wall:

like-sectiona storming fulcrum sectors, an arouateupperrim Eoformingapower sector, laterally extending hubs it inwhichare-located.thecentersof the julcrumand power, sectors '49 and 59,. and a track521along which an adjusting weight assembly 53" may be positioned andsecured: As

in 'the'preceding example, thependulum is sus--v pended-from-the sideofa sector guide 54 by means of fulcrum ribbonsbdwhose lower ends areattached to the fulcrumsectors 43; Forces from the loadsj to be, weighedby the pendulumare transmitted through a steelyard rodfitto a power.

ribbon 5'! that overlies the power sector 56.

The track similar to thetrack 28. of themeceding example, has externalmachined surfaces and-a longitudinal slot that intersects a hole drilledparallel tothe. machined surfaces: The,

adjustingweigh-t ttwincludes a pair :of major weights58 cast of leadonthe legs of a U-shaped hracketfid-the bottom of which rests against thetrack :52 with the weights 58 disposed onv either sideofi the track. Thebracket 59 is held in place by a pair: of bolts that pass through holesin the bracket, through the-slot in the track 52 and en-.

gage-a cylindrical nut til inserted in theidrilled.

holes A secondary track. 6 I that is Welded to the U-ishapedbracketeflextends in. the plane of. the pendulum, and carries-a minor adjustingweight,

assembiy filla The minor weight assembly com- 131156558.-U-shaped--;carrier 63 whole legs are notched toslide over thetraek tiand that embraces between its sides a subweight 6d, a spring 55 andanut' fifi thatare held in clamped position by a setscrew 8?.Thisassembly is similar to the minorweight assembly tfifshown inFiguresIII and IV. This assembly permits the: subweight .61! A g toxbe adjustedparallel -to thetrackfi andthe; ininor weight assembly $2 tobe adjustedalong.

theatrack 6 4;

.While .a construction that includes the track alongwhich the adjustingweights arepositioned as an integral part-of the pendulum providestheutmost in rigidity fora given weight of material andthus contributes tothe excellence of, the

pendulum as a weighing elemcntit isnnotineces sary that the, pendulum.be, constructed with inc-.1; tegralwtracksn Neither; is it. necessarythat the secondary track bemounted onj-the, adjusting weightassembly oreven be a part-of thatassembly. A third example otpendulum in whichtheadjustments, are substantially 7 independent of each other and thetracks are each attached to thezsectorsu is illustrated inFi ure VII,"Inmthis example a casting. 68 having iulcrum sectors. 69, a powersectorv l0 and laterally extending bosses, 1 l, :isprovided1vvithadownwardly extcndingim;

weight? :13 'isiiadjustably. secured. l. A.. sc.c0ndary re ded stemrf lcarryi g a secondary. weight. I5. issprovlded. for makinghalf capacityadjust-1; ments in the, scale. s. In this examplethe threaded, stems J2and 14 form major and. secondary tracks alongiwhich the adjustingweights are, positioned;

This pendulum corresponds, in iunctiom -adjustef ment power.,and initialpull tomthependulum...

illustrated-indetail-inFigure. III,

If it is desiredto reduce theinitial pull of. this:-

pendulum without reducing its poweriitj. may be modified in exactly thesame way that the high; initial, pull pendulum l was modifiedto .formthe low-initial; pull vpendulum. 5811. e.,,. by extcnding. the.fulcrum-and .powersectors. downwardly and. around. toward'-' the. majorwelght stem 12.. and. allowing. the pendulum: to swing in v ,to.\1var dthe;

sector guidepat light load.

In each of the .pendulums, illustrated ,a. wide; range of power isavailable by, merelymoving as weight alonga track. In. some of theexamples. the change, in power does not.affecttheinitiala pull. In theexample shown in FigureV, aninr.

. crease in power is accompanied by a decrease in: initial pull. In apendulum constructed accord-1,1. ing tojthedesign. shown in, Figure Vtheinitial pull and the, power maysimultaneously be in-.. creased byincreasing theweight of theacljuste. ingweight assembly 53.: If the.weight. is in creasedand at the sametimeis moved upwardly.

likema-nner the.,power of the pendulum maybe increased without, changingthe initial pull if the weight of the .assembly-lsincreascd andjt. ismoved-downwardly along, .the; .track 152... The changedn pull and powerisdirected proportional. tothe change in total; mass of the pendulum, if

mass is added or taken awayiromthe adjusting weight The chhflgeinpowerandinitialpull are also: directly proportional tolthe, distances.that

theweight assemblies aremoved along the tracksn Because ofthetranscendental, nature of .trlgo-,:- nometric functions the designofa pendulum-that; will rotate through equaliangles. for equal .in-..

crements of load is not subject toanexact so; lution... The .deviations,in a good design, v are.

apparent only. if the. calculations. are carried out to five or moresignificantfigures, The restor in .moment1-.of; thep ndulumsillust atedlat eXam-PleS;,lS, pronortionalito; the hor zontal .di

tance between; a vertical. plane containing the,

fulcrum ribbons and the center of. gravity.of then pendulum;Whencomputing thelocatloniof the-, center .of;gravity, that portioncttheweight of;

the compensating bars,,yoke andirackj thatis: carried byeach pendulum isconsidered asbeing concentrated atthe. turning center of, the pendu:min. i- .e thejcenter oi curyature. of theiulcrum sectors. The.distance-, from theiulcrum plane torthe centerc'oijgravity..of thependulum,.,.as the, pendulum. swings through various angles, is equal tothe radius .of, the fulcrum, sectors. plus the product of thedistancebetween the turning cen.-.

ter and the centerof gravity and the sine of vthe angle between thevertical and the line from the turning center to the center of gravity.Thus the counterbalancing moment of the pendulumgis equal toqa constant,plus a junction of the-sine. of,-:theangle. This function .is notlinear; with;

respect to angle and, therefore, the effective power arm of the loadmust vary in such a manner that it compensates for the nonlinearity ofthe counterbalancing moment.

From an examination of Figure III or V it will be noticed that the powerribbons [2 or 51 are not exactly vertical, but tend to diverge from eachother as they leave the yoke on the steelyard rod. The tension in eachof the power ribbons, there being two in each scale assembly. is equalto half of the load applied to the yoke divided by the cosine of theangle between the power ribbon and the vertical. The moment arm at whichthe pull of the power ribbon is applied to the pendulum is the distance,measured perpendicular to the power ribbon, from the ribbon to the pointof contact between the fulcrum sectors and the sector guide. Bycombining the increase in tension due to the angularity of the powerribbons with the moment arm of the ribbon, i. e. dividing theperpendicular distance from the power ribbon to the points of contact ofthe fulcrum sectors by the cosine of the power ribbon angle, theefiective horizontal moment arm which may be called the power arm of thependulum is obtained. By suitably selecting the distance between thecenters of the fulcrum and the power sectors as well as the diilferencein radii of the sectors it is possible to match the power arm of thependulum against the counterbalancing moment arm to obtain substantiallyequal increments of angle for equal increments of load. Thisrelationship holds when the distance between the centers of curvature ofthe sectors is slightly less than one-third of the distance between theperipheries of the sectors measured along a line passing through thecenters of the sectors.

It has further been found that the tracks 28, 52 or 12 should bevertical or substantially so when the power arm of the pendulum is amaximum. This relationship is not exact because the angle between thepower ribbons and the vertical changes with load and the angularity ofthe 'power ribbon is increasingly more effective in affecting thependulum as the line of centers of the sectors departs from thehorizontal. These considerations fix the direction of the tracks but donot determine their location with respect to the sectors. Calculationsconfirmed by experimentindicate that the locus of the centers of gravityof the pendulum to which locus the tracks 28, 52 or 12 are parallel,intersects the line of centers of the sectors on the side opposite thepower sectorat a distance beyond the centers which is a function of theradii of the sectors and the eccentricityof the power sectors withrespect to the fulcrum sectors. The position'of this locus wasdetermined experimentally by adjusting the pendulum for correctoperation with the weight near the bottom of the track, locating thecenter of gravity, then moving the weight to the top of the track andagain adjusting ,it for linear operation. The two locations of thecenter'of gravity thus determined fixes the locus for the tracks. In theexample shown in Figure III the track is made to coincide with the locusandthe major adjusting weight assembly is made of such massand shapethat the result ant center ofgravity 'lieson the track '28. In

so as to bring the resultant center of gravity jfonto the requiredlocus.

10 Efiect of adjustments The effect of making variousadjustmen-ts on thependulum is illustrated in Figure VIII. This figure shows a graph of thepull on the steelyard rod plotted as ordinates against the correspondingangular rotation of the pendulum as abscissa; The operating range forthe pendulum shown in minus twenty degrees andplus forty degrees.

Considering the pendulum of Figure III, if the weight assembly 29 islowered along the track 28 or if the subweight 38 is moved downwardlythrough the Uv-shaped holder 31, the power of the pendulum is increasedso that it operates.

along a line 18l9 that intersects the original line 16'l1 at zerodegrees. Likewise if either of the weights are raised the operation isthen along the line 18-436. The efiect of moving the weight parallel tothe track is merely to change the slope of the line without introducingany curvature into it. This means that if the scale is assembled andbalanced with the indicator at zero andthe track vertical that a fullload may be applied and the scale corrected at full capacity by merelymoving the weight along the line parallel to the track until the fullscale reading is correct, and that such adjustment will 'not' aggravatethe error at half capacity, nor will it change the condition of balanceof the scale at zero.

If the minor weight assembly 36 is moved along the secondary track 35 itproduces several effects.

The first of these efiects, observed at zero, is a change in initialpull. If the Weight is moved outwardly along the track 35, the initialpull is increased so that after the change it is represented bythe-point 8| in Figure VIII. Suppose, for the moment, that the track 35extends per pendicular to the track 28 so that the vertical position ofthe center of gravity remains un-' changed. Then as the pendulum swingsupwardly so that the track tends to point inan upward direction, theeil'ectiveness of the change continuously decreases with increase-inangle'so that the scale instead of operating along a straight line suchas the line !8|1 operates along a curve 8l--8283. However, forconvenience in adjusting the scale, since this curvature is used tosecure correct half capacity readings; it is desirable that the line8l83, the chord of the curve 8l8283, remains parallel to the line 18-11because the line may be shifted vertically without changing slope orcurvature by changing the initial pull. The line 8 l-83 can be pivotedabout the point 8i by moving either the whole adjustable weight assembly29 or the subweight 38 downwardly which has the-effect of line 8l'.-83'is brought up to the position-8I'B4.

To avoid making two adjustments in order-to introducecurVature-intotheline and yet maintain the same slope of the line between the end pointsthe track 35-is given a downward slope when the pendulum is at zero sothat thetwo adjustments are made simultaneously when the weight is movedalong the track. Thus, in. the example shown in Figure III the change inpull produced by sliding the minor weight assembly ates-4st along thetrack 35 is the same whether the pendulum is at zero (shown in solidlines) or whether the pendulum is at full scale position shown in brokenlines. The angle of the track 35 as measured from a horizontal line ateach of these two pendulum positions is not the same because the powerhorizontal projection of the track 35 at these positions must beproportional to the arms at which the ribbon [2 acts rather than beingequal. If the adjusting weight is moved inwardly toward the largerweight the initial pull is decreased and the curve bows downwardly.

- The rise in the curve 81-82-83 over'its chord 8l-'-83 is approximatelyone-tenth of the change in initial pull represented by the distance18--8 l. Thisrelationship is used in adjusting thependulum to remove anerror at half capacity by shifting the secondary weight assemblies 36along the tracks 35 until the change in scale indication isapproximately ten times as great and in the opposite direction as theobserved error athalf load. When the load is taken off the scale and itrebalanced at zero by a change in the initial pulladdition or removal ofweight from a loading box-the scale will be found to be in reasonablygood adjustment. A repetition of the adjusting process, 1. e, applying afull capacity load and adjusting the subweight 38 to bring the indicatorinto correct registry, then reducing the load to half and adjusting theminor weight assembly along the track 35 according to the ten to onerelation and finally rebalancing at zero will, in most instances, bringthe scale into as close an adjustment as may be made.

The pendulum shown in Figure V whose operating range is from minustwenty degrees to plus forty degrees is adjusted by a similar procedure.However, because the track 52 is not vertical when the indicator is atzero, the initial pull is changed when any change in power is made.Therefore, if a, scale embodying the pendulum of Figure V is balanced atzero and found to be in error with a full capacity load. the error atfull capacity must be removed by shifting the subweight 64 to eliminatetwo-thirds of the error and changing the initial pull to correct theremaining one-third. Then the scale is loaded to half capacity and theerror in indication noted. The minor weight assembly 62 is moved alongthe track 6| until the error in indication at half capacity is reversedin sign and increased to about ten times its original amount. The scaleis then brought to zero and rebalanced. This sequence of steps removesmost of the error and one or two repetitions of the sequence will serveto remove the residual error.

The adjustments for either pendulum are easy to make-and are notparticularly critical because in each instance a comparatively smallmass is moved a large distance to effect a small change in position ofthe center of gravity of the pendulum assembly. The locus of movement ofthe adjusting Weights is such that movement of one weight changes thecapacity or power of the pendulum without affecting its linearity, whilemovement of the other weight changes the linearity ,without changing thepower or capacity of the pendulum.

The one piece construction provides exceptional strength and rigidity aswell as uniform temperature characteristics so that change errors arereduced to a minimum. The increased rigidity of the improved pendulumpermits a much better distribution of its weight so that most of theweight is efiective in providing either initial pull or power and verylittle of it is located in the-- upper part of the pendulum-thesectors-where dulum may be designed so that when the indi cator is atzero the locus of the centers of gravity, the line parallel to the track52 for example, intersects the vertical plane of the fulcrum ribbons.Weight added to the pendulum at this H intersection will'not change theinitial pull because it is added at a point immediately below the pointof support of the pendulum nor'will'it change the linearity of thependulum because the addition of weight at the intersection of the lineand the plane is merely equivalent to moving the adjusting weightsdownwardly along the track at the same time that their magnitudeisincreased.

Various modifications of the improved pendulum may be made'to meet thevarious requirements of initial pull and power, and still maintain theadvantage of independence of adjustments.

Having described the invention, I claim:

1. A pendulum for a weighing scale, the pendulum comprising a fulcrumsector having a center, a power sector having a center that is displacedfrom the center of the fulcrum sector, a rectilinear track that isgenerally perpendicular to the line connecting the centers of the flll'.crum and power sectors, a weight movable along the track, a secondrectilinear track having a fixed acute angular relation to the firstrectilinear track, and a second weight movable along the second track.

2. A pendulum for a weighing scale, the pendulum comprising a member inwhich is formed a fulcrum sector, an eccentric power sector and arectilinear track that is generally perpendicular to the line of centersof the power and fulcrum sectors; a weight movable along the track, asecond track positioned at an acute angl with respect to the firsttrack, and a weight movable along the second track.

3. In a pendulum for a weighing scale, a pendulum body having an axis ofrotation, a power sector to which load forces may be tangentiallyapplied and which is eccentric to the turning axis to vary the effectivemoment arm of the load force as the pendulum turns on its axis, a secondsector to which force may be tangentially applied and which issubstantially concentric with the turning axis, a rectilinear track thatstands vertical when the line of action of the load force is generallyperpendicular to the line of centers of the sectors, and a second trackarrangedat-an angle to the first track such that at each end of thependulum travel the horizontal projection of the second track issubstantially proportional to the effective moment arm ofthe load'force. 1

4. Apendulum body according to claim 3 having a weight mounted on therectilinear track and having said second track formed on said weight.

5. In an automatic weighing scale, in combination, a pendulum having asector to which load forces are tangentially applied, said sector beingarranged eccentric to the turning axis of the pendulum. so that themomentarm of the load force varies with the position of the pendulum, anadjusting weight, and a track on the pendulum to support the weight, thetrack being arranged with respect to the sector so that at twopreselected and spaced apart positions in the range of travel of thependulum the horizontal projections of the track are proportional to thecorresponding moment arms of the load forces 6. In an automatic weighingscale, in combination, a pendulum having a sector to which load forcesare tangentially applied, said sector being arranged eccentric to theturning axis of 10 1,088,321

the pendulum so that the moment arm of the load force varies with theposition of the pendulum, an adjusting weight, a track on the pendulumto support the weight, the track being arranged with respect to thesector so that at the 15 2,294,819

ends of the pendulum travel the horizontal projections of the track areproportional to the corresponding moment arms or the load forces.

LAWRENCE S. WILLIAMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 146,944 Parr Jan. 27, 1874655,147 De Vilbiss July 31, 1900 Charet Feb. 24, 1914 1,454,047 EmeryMay 8, 1923 1,515,034 Griswold Nov. 11, 1924 1,890,977 Kelly Dec. 13,1932 2,217,244 Williams Oct. 8, 1940 Williams Sept. 1, 1942

